Manuscript of the Introit of the Mass (from Psalm 42), Florence, Italy.Excerpt from the missal, a liturgical book, of the Sint-Pieters Abbey (Ghent), from the 13th century. Manuscript preserved in the Ghent University Library.[1]
A liturgical book, or service book, is a book published by the authority of a church body that contains the text and directions for the liturgy of its official religious services.